Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

The present application provides a shaft speed monitoring system for a
pulse detonation combustor with a number of combustion tubes and
positioned about a shaft of a pulse detonation turbine engine. The shaft
speed monitoring system may include one or more shaft sensors positioned
about the shaft and a control in communication with the shaft sensors to
determine a number of shaft speed fluctuations related to each of the
combustion tubes.

Claims:

1. A shaft speed monitoring system for a pulse detonation combustor with
a number of combustion tubes and positioned about a shaft of a pulse
detonation turbine engine, comprising: one or more shaft sensors
positioned about the shaft; and a control in communication with the one
or more shaft sensors to determine a plurality of shaft speed
fluctuations related to each of the number of combustion tubes.

2. The shaft speed monitoring system of claim 1, wherein the one or more
shaft sensors determine the speed and/or the acceleration of the shaft.

3. The shaft speed monitoring system of claim 1, wherein each of the
number of combustion tubes is pulsed and wherein the one or more shaft
sensors detect a shaft speed fluctuation caused thereby.

4. The shaft speed monitoring system of claim 1, wherein the control
monitors a plurality of cycle groups of the shaft speed fluctuations over
time.

5. The shaft monitoring system of claim 4, wherein the control monitors
the plurality of cycle groups in a plurality of windows.

6. The shaft monitoring system of claim 1, wherein the control provides a
feedback signal to the pulse detonation combustor.

7. The shaft monitoring system of claim 1, wherein each of the number of
combustion tubes comprises a combustion zone therein.

8. The shaft monitoring system of claim 1, wherein the one or more shaft
sensors comprise original equipment of the pulse detonation turbine
engine.

9. A method of monitoring the operation of a number of pulse detonation
combustion tubes via shaft speed in a pulse detonation turbine engine,
comprising: sensing the speed or acceleration of the shaft; determining a
plurality of cycle groups of speed fluctuations based upon shaft speed
over time; and comparing the plurality of the cycle groups to determine
variations therein.

10. The method of claim 9, wherein the plurality of cycle groups are
compared within a plurality of windows.

11. The method of claim 9, wherein each speed fluctuation within a cycle
group corresponds to one of the number of pulse detonation combustion
tubes.

12. The method of claim 11, wherein a variation in one speed fluctuation
of a cycle group indicates that the corresponding pulse detonation
combustion tube is operating differently than the other combustion tubes.

13. The method of claim 11, wherein a variation in one speed fluctuation
of a cycle group in a plurality of windows indicates that the
corresponding pulse detonation combustion tube is operating differently
than the other combustion tubes.

14. The method of claim 9, further comprising the step of generating one
or more feedback signals to the pulse detonation turbine engine.

15. The method of claim 9, further comprising the steps of altering one
or more pulse detonation combustion tube operational parameter based upon
the determined variations.

16. The method of claim 15, wherein the step of altering one or more
pulse detonation combustion tube operational parameters comprises
altering an inlet air mass flow, a fill fraction, a purge fraction,
and/or a fuel/air equivalence ratio.

17. The method of claim 9, further comprising the step of determining a
likelihood of combustion tube failure based upon the determined
variations.

18. The method of claim 9, further comprising the step of determining one
or more combustion tube maintenance needs based upon the determined
variations.

19. The method of claim 9, further comprising the step of determining one
or more turbine loading needs based upon the determined variations.

20. A shaft speed monitoring system for a pulse detonation combustor with
a number of combustion tubes and positioned about a shaft of a pulse
detonation turbine engine, comprising: one or more shaft sensors
positioned about the shaft to determine the speed and/or the acceleration
of the shaft; and a control in communication with the one or more shaft
sensors to determine a plurality of cycle groups of shaft speed
fluctuations over time related to each of the number of combustion tubes
and to provide a feedback signal to the pulse detonation combustor.

Description:

TECHNICAL FIELD

[0001] The present application relates generally to pulse detonation
turbine engines and more particularly relates to a pulse detonation
turbine engine using turbine shaft speed for prognostics and monitoring
of a pulse detonation combustor and the individual combustion tubes
therein.

BACKGROUND OF THE INVENTION

[0002] Recent developments with pulse detonation combustors and engines
have focused on practical applications such as generating additional
thrust/propulsion for aircraft engines and to improve overall performance
in ground-based power generation systems. Known pulse detonation
combustors and engines generally operate with a detonation process having
a pressure rise as compared to conventional engines operating with a
constant pressure deflagration. Specifically, air and fuel are mixed
within a pulse detonation chamber and ignited to produce a combustion
pressure wave. The combustion pressure wave transitions into a detonation
wave followed by combustion gases that produce thrust as they are
exhausted from the engine. As such, pulse detonation combustors and
engines have the potential to operate at higher thermodynamic
efficiencies than generally may be achieved with conventional
deflagration-based engines.

[0003] Monitoring the state of the pulse detonation combustors and the
individual combustion tubes therein is important for load balancing of
the pulse detonation turbine engine and for determining the overall
health of the pulse detonation combustor. Currently, the only means for
accessing the state of an individual combustion tube of a pulse
detonation combustor is to position instrumentation directly within the
combustion tube. Due to the extreme temperatures, pressures, and
vibrations therein, however, such instrumentation within the combustion
tubes may have a life significantly shorter than may be required for the
commercial application of the overall pulse detonation turbine engine.

[0004] There is thus a desire for an improved pulse detonation turbine
engine design. Such an improved design preferably would enable monitoring
of the individual combustion tubes and the pulse detonation combustor as
a whole without subjecting the instrumentation to the extreme
temperatures, pressures, and vibrations generally present therein so as
to provide a longer service lifetime with less downtime while maintaining
accurate readings therein.

SUMMARY OF THE INVENTION

[0005] The present application thus provides a shaft speed monitoring
system for a pulse detonation combustor with a number of combustion tubes
and positioned about a shaft of a pulse detonation turbine engine. The
shaft speed monitoring system may include one or more shaft sensors
positioned about the shaft and a control in communication with the shaft
sensors to determine a number of shaft speed fluctuations related to each
of the combustion tubes.

[0006] The present application further provides a method of monitoring the
operation of a number of pulse detonation combustion tubes via shaft
speed in a pulse detonation turbine engine. The method may include the
steps of sensing the speed or acceleration of the shaft, determining a
number of cycle groups of speed fluctuations based upon shaft speed over
time, and comparing the cycle groups to determine variations therein.

[0007] The present application further provides a shaft speed monitoring
system for a pulse detonation combustor with a number of combustion tubes
and positioned about a shaft of a pulse detonation turbine engine. The
shaft speed monitoring system may include one or more shaft sensors
positioned about the shaft to determine the speed and/or the acceleration
of the shaft and a control in communication with the shaft sensors to
determine a number of cycle groups of shaft speed fluctuations over time
related to each of the combustion tubes and to provide a feedback signal
to the pulse detonation combustor.

[0008] These and other features and improvements of the present
application will become apparent to one of ordinary skill in the art upon
review of the following detailed description when taken in conjunction
with the several drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a side cross-sectional view of a known pulse detonation
combustor.

[0010]FIG. 2 is a schematic view of a known pulse detonation turbine
engine with a number of pulse detonation combustors.

[0011]FIG. 3 is a graph showing shaft speed fluctuations as a measure of
shaft speed and time,

[0012]FIG. 4 is a graph showing shaft speed fluctuations as a measure of
shaft speed and time

DETAILED DESCRIPTION

[0013] As used herein, the term "pulse detonation combustor" refers to a
device or a system that produces both a pressure rise and a velocity
increase from the detonation or quasi-detonation of a fuel and an
oxidizer. The pulse detonation combustor may be operated in a repeating
mode to produce multiple detonations or quasi-detonations within the
device. A "detonation" may be a supersonic combustion in which a shock
wave is coupled to a combustion zone. The shock may be sustained by the
energy release from the combustion zone so as to result in combustion
products at a higher pressure than the combustion reactants. A
"quasi-detonation" may be a supersonic turbulent combustion process that
produces a pressure rise and a velocity increase higher than the pressure
rise and the velocity increase produced by a sub-sonic deflagration wave.
For simplicity, the terms "detonation" or "detonation wave" as used
herein will include both detonations and quasi-detonations.

[0014] Exemplary pulse detonation combustors, some of which will be
discussed in further detail below, include an ignition device for
igniting a combustion of a fuel/oxidizer mixture and a detonation chamber
in which pressure wave fronts initiated by the combustion coalesce to
produce a detonation wave. Each detonation or quasi-detonation may be
initiated either by an external ignition source, such as a spark
discharge, laser pulse, heat source, or plasma igniter, or by gas dynamic
processes such as shock focusing, auto-ignition, or an existing
detonation wave from another source (cross-fire ignition). The detonation
chamber geometry may allow the pressure increase behind the detonation
wave to drive the detonation wave and also to blow the combustion
products themselves out an exhaust of the pulse detonation combustor.
Other components and other configurations may be used herein

[0015] Various combustion chamber geometries may support detonation
formation, including round chambers, tubes, resonating cavities,
reflection regions, and annular chambers. Such combustion chamber designs
may be of constant or varying cross-section, both in area and shape.
Exemplary combustion chambers include cylindrical tubes and tubes having
polygonal cross-sections, such as, for example, hexagonal tubes. As used
herein, "downstream" refers to a direction of flow of at least one of the
fuel or the oxidizer.

[0016] Referring now to the drawings, in which like numbers refer to like
elements throughout the several views, FIG. 1 shows a generalized example
of a pulse detonation combustor 100 as may be described and used herein.
The pulse detonation combustor 100 may extend from an upstream head end
115 that includes an air inlet 110 and one or more fuel inlets 120 to an
exit nozzle 130 at an opposed downstream end 135. A combustion tube 140
may extend from the head end 115 to the nozzle 130 at the downstream end
135. The combustion tube 140 defines a combustion zone 150 therein. A
casing 160 may surround the combustion tube 140. The casing 160 may be in
communication with the air inlet end 110 at the head end 115 and may
extend to or beyond the nozzle 130 at the downstream end 135. The casing
160 and the combustion tube 140 may define a bypass duct 170
therebetween. Although only one combustion tube 140 is shown, any number
may be used. Other components and other configurations may be used
herein.

[0017] The air inlet 110 may be connected to a source of pressurized air
such as a compressor. The pressurized air may be used to fill and purge
the combustion chamber 150 and also may serve as an oxidizer for the
combustion of the fuel. The air inlet 110 may be in communication with an
air valve 180 and the combustion zone 150. Likewise, the fuel inlet 120
may be connected to a supply fuel that may be burned within the
combustion zone 150. The fuel may be injected into the combustion zone
150 so as to mix with the airflow.

[0018] An ignition device 190 may be positioned downstream of the air
inlet 110 and the fuel inlet 120. The ignition device 190 may be
connected to a controller so as to operate the ignition device 190 at
desired times and sequences as well as providing feedbacks signals to
monitor operations. As described above, any type of ignition device 190
may be used herein. The fuel and the air may be ignited by the ignition
device 190 into a combustion flow so as to produce the resultant
detonation waves. A portion of the airflow also may pass through the
bypass duct 170. This portion of the airflow may serve to cool the
combustion tube 140, the combustion zone 150, and the nozzle 130. Other
components and other configurations may be used herein. Any type of pulse
detonation combustor 100 may be used herein.

[0019]FIG. 2 shows a generalized example of a pulse detonation turbine
engine 200 using the pulse detonation combustor 100. Generally described,
the pulse detonation turbine engine 200 may include a compressor 210 to
compress an incoming flow of air. The compressor 210 may be in
communication with an inlet system 220 with a number of the air valves
180. Each inlet valve may be in communication with a combustion tube 140
as described above so as to mix the compressed flow of air with a
compressed flow of fuel for combustion therein. The pulse detonation
combustor 100 may be in communication with a turbine 230 via the nozzles
130 or other type of plenum. The hot combustion gases from the pulse
detonation combustors 100 drive the turbine 230 so as to produce
mechanical work. Other configurations and other components may be used
herein. Any type of pulse detonation turbine engine 200 may be used
herein with any type of pulse detonation combustor 100.

[0020]FIG. 2 also shows a shaft speed monitoring system 240. The
mechanical work produced in the turbine 230 drives the compressor 210 via
a shaft 250. The shaft 250 also may drive an external load such as an
electrical generator and the like. The shaft speed monitoring system 240
may include a number of sensors 260 positioned about the shaft 250 so as
to monitor the speed of the shaft 250 and hence the speed of the
compressor 210 and the turbine 230. The sensors 260 may monitor shaft
speed and/or acceleration. The sensor 260 may be of conventional design
and may have enough time resolution to resolve shaft speed or
acceleration fluctuations due to tube combustion cycles. The sensor 260
may be original equipment on the pulse detonation turbine engine 200.

[0021] The sensors 260 may be in communication with a control 270. The
control 270 may monitor the output of the sensors 260 and the condition
of the overall pulse detonation turbine engine 200 and the individual
components thereof. The control 270 may be of conventional design and may
be any type of programmable logic controller and the like. Multiple
controls 270 may be used herein. Other types of control devices may be
used herein. The shaft speed monitoring system 240 may use other
components and other configurations.

[0022] The individual combustion tubes 140 of the pulse detonation
combustor 100 within the overall pulse detonation turbine engine 200
generally pulse on a staggered basis. For example, the pulse detonation
combustor 100 may have twelve (12) combustion tubes 140, although any
number of combustion tubes 140 may be used. The goal herein is to ensure
that each of the combustion tubes 140 is operating in a consistent
manner. As such, the speed of the shaft 250 may be monitored by the shaft
speed monitoring system 240 for combustion tube correlated variations in
a number of speed fluctuations 275 via an appropriate algorithm.

[0023] For example, FIG. 3 shows an example of the speed fluctuations 275
of the shaft 250 in terms of the speed of the shaft 250 in revolutions
per minute with respect to time in seconds. Given the use of the pulse
detonation combustor 100 with the twelve (12) combustion tubes 140, a
number of twelve (12) speed fluctuation cycles may be evaluated. As is
shown, a first cycle group 280 may be evaluated in a first window 290 and
a number of further cycle groups 300 may be evaluated in a number of
further windows 310. In this example, the further cycle group 300 may be
cycle group 6,097 and may be evaluated in a second window 320. Likewise,
a further cycle group 300 may be cycle 28,926 and may be evaluated in a
third window 330. Any number of further cycle groups at any cycle number
in any number of further windows 310 may be used herein.

[0024] As is shown in the example of FIG. 3, a fourth combustion tube 140
may be operating differently from the remaining combustion tubes 140 as
indicated by the different speed fluctuation 340. This information may be
used, for example, as a feedback signal 350 by the control 270 of the
shaft speed monitoring system 240 to the pulse detonation combustor 100
or elsewhere within the pulse detonation turbine engine 200 and the like.
The feedback signal 350 may promote balanced turbine loading by, for
example, adjusting the time, fuel pressure, and/or inlet air mass flow of
the fourth tube 140. Altering the inlet air mass flow may be done via
adjustable restrictor plates or geometry so as to vary the effective area
of the airflow path and the like. Such a variation may impact on any
number of operational parameters such as fill fraction (the fraction of
the combustion tube filled with the fuel-air mixture), purge fraction
(the fraction of the combustion tube purged with unfueled air), fuel/air
equivalence ratio, etc. Real time monitoring and feedback thus may be
provided herein.

[0025]FIG. 4 shows a similar graph of the speed fluctuations 275 in terms
of speed versus time. In this example, the change in the speed
fluctuations 340 of the fourth combustion tube 140 shows that the
operation of the fourth combustion tube 140 is deteriorating over time as
compared to the remaining combustion tubes 140. Specifically, the speed
fluctuations 275 are changing over time as compared to the first cycle
group 280 in the first window 290 and the further cycle groups 300 in the
further windows 310. This information may be used as part of a prognostic
health monitoring system such that the shaft speed monitoring system 240
may estimate when tube failure may be likely to occur and also to
schedule maintenance prior to such failure. Additionally, this
information may be used to modify the operation of the combustion tube
140 to provide the same turbine loading therein as the other combustion
tubes 140 until maintenance may be performed. Other components and other
configurations may be used herein.

[0026] The control 270 of the shaft speed monitoring system 240 thus may
use the speed and acceleration of the shaft 250 as determined by the
sensors 260, along with an appropriate algorithm, to estimate or
determine the operability of the pulse detonation combustor 100 and the
individual combustion tubes 140 therein. This information may be used to
predict failure modes for prognostic health monitoring, and to provide
feedback to the overall control 270. Moreover, because shaft speed is
already a sensed quantity, this monitoring approach does not add
complexity or additional instrumentation. Likewise, the use of
instrumentation within the combustion tubes 140 themselves may be
avoided. Hence, the short lifetime thereof may be avoided while
maintaining highly accurate monitoring herein.

[0027] It should be apparent that the foregoing relates only to certain
embodiments of the present application and that numerous changes and
modifications may be made herein by one of ordinary skill in the art
without departing from the general spirit and scope of the invention as
defined by the following claims and the equivalents thereof.